From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9C28EC0001 for ; Mon, 15 Mar 2021 21:48:30 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 895AB43144 for ; Mon, 15 Mar 2021 21:48:30 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -0.202 X-Spam-Level: X-Spam-Status: No, score=-0.202 tagged_above=-999 required=5 tests=[BAYES_40=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Authentication-Results: smtp2.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=dashjr.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id j7ry9kdkY4U5 for ; Mon, 15 Mar 2021 21:48:29 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from zinan.dashjr.org (zinan.dashjr.org [192.3.11.21]) by smtp2.osuosl.org (Postfix) with ESMTP id 4E3DC4000B for ; Mon, 15 Mar 2021 21:48:29 +0000 (UTC) Received: from ishibashi.lan (unknown [12.190.236.209]) (Authenticated sender: luke-jr) by zinan.dashjr.org (Postfix) with ESMTPSA id 6965238A009E for ; Mon, 15 Mar 2021 21:48:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=dashjr.org; s=zinan; t=1615844908; bh=YerwjjIZG6WUFg8EYDHdazr9qu9MyXzzihWQyozSz3E=; h=From:To:Subject:Date; b=LwaxAJMXX0WfHLZ+Pk+n1/n70BH/1DIiPjySjvf6y5+cuWrptmVE1NruwKZmaLhy5 DTBrVoR8YeGNEEPylRBr74hcQ+gG70gxSbXtBvoXnMSOKF3E1iqMlbbVDolJPdnpWY 0hAkE4mh7BOd5fpq54JPHMbClFzsJEpQbJGyAAfQ= X-Hashcash: 1:25:210315:bitcoin-dev@lists.linuxfoundation.org::=hqcgzBkQV2Nt/++:a5EzX From: Luke Dashjr To: Bitcoin Protocol Discussion Date: Mon, 15 Mar 2021 21:48:15 +0000 User-Agent: KMail/1.9.10 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <202103152148.15477.luke@dashjr.org> Subject: [bitcoin-dev] PSA: Taproot loss of quantum protections X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Mar 2021 21:48:30 -0000 I do not personally see this as a reason to NACK Taproot, but it has become clear to me over the past week or so that many others are unaware of this tradeoff, so I am sharing it here to ensure the wider community is aware of it and can make their own judgements. Mark Friedenbach explains on his blog: https://freicoin.substack.com/p/why-im-against-taproot In short, Taproot loses an important safety protection against quantum. Note that in all circumstances, Bitcoin is endangered when QC becomes a reality, but pre-Taproot, it is possible for the network to "pause" while a full quantum-safe fix is developed, and then resume transacting. With Taproot as-is, it could very well become an unrecoverable situation if QC go online prior to having a full quantum-safe solution. Also, what I didn't know myself until today, is that we do not actually gain anything from this: the features proposed to make use of the raw keys being public prior to spending can be implemented with hashed keys as well. It would use significantly more CPU time and bandwidth (between private parties, not on-chain), but there should be no shortage of that for anyone running a full node (indeed, CPU time is freed up by Taproot!); at worst, it would create an incentive for more people to use their own full node, which is a good thing! Despite this, I still don't think it's a reason to NACK Taproot: it should be fairly trivial to add a hash on top in an additional softfork and fix this. In addition to the points made by Mark, I also want to add two more, in response to Pieter's "you can't claim much security if 37% of the supply is at risk" argument. This argument is based in part on the fact that many people reuse Bitcoin invoice addresses. First, so long as we have hash-based addresses as a best practice, we can continue to shrink the percentage of bitcoins affected through social efforts discouraging address use. If the standard loses the hash, the situation cannot be improved, and will indeed only get worse. Second, when/if quantum does compromise these coins, so long as they are neglected or abandoned/lost coins (inherent in the current model), it can be seen as equivalent to Bitcoin mining. At the end of the day, 37% of supply minable by QCs is really no different than 37% minable by ASICs. (We've seen far higher %s available for mining obviously.) To conclude, I recommend anyone using Bitcoin to read Mark's article, my thoughts, and any other arguments on the topic; decide if this is a concern to you, and make your own post(s) accordingly. Mark has conceded the argument (AFAIK he doesn't have an interest in bitcoins anyway), and I do not consider it a showstopper - so if anyone else out there does, please make yourself known ASAP since Taproot has already moved on to the activation phase and it is likely software will be released within the next month or two as things stand. Luke